Hydraulic valve play compensating element for reciprocating-piston internal combustion engines

ABSTRACT

A reciprocating-piston internal combustion engine which operates on the four-stroke cycle, having a crankcase and having at least one cylinder which is arranged in said crankcase and in which a piston is guided by a crankshaft, having at least one cylinder head which closes off the cylinder and the intake and exhaust channels which are controlled by at least in each case one intake and exhaust valve loaded by a valve spring, which intake and exhaust valves can be actuated by transmission elements driven by a camshaft, and having a hydraulic valve play compensating element ( 5 ) which is installed in at least one of the transmission elements or in a component, which is installed in the transmission element, between the camshaft and at least one intake and/or exhaust valve, which hydraulic valve play compensating element has a working piston ( 8 ), a cylinder housing ( 7 ) which interacts with the working piston ( 8 ), a restoring spring ( 18 ) which is installed in between, and a check valve which delimits a high-pressure chamber ( 19 ) and the valve closing body ( 12 ) of which corresponds to a valve seat ( 11 ) on the working piston ( 8 ). The valve closing body ( 12 ) has a partial spherical surface ( 13 ) in a region of the valve seat ( 11 ), and a ratio of the diameter of the working piston ( 8 ) to twice the radius of the partial spherical surface ( 13 ) is ≦2.

FIELD OF THE INVENTION

A reciprocating piston internal combustion engine working with the four stroke method and comprising a crankcase and at least one cylinder arranged in said crankcase, in which cylinder a piston is guided by a crankshaft, said engine further comprising at least one cylinder head closing said cylinder, inlet and outlet channels of said cylinder head being controlled in each case by at least one inlet and outlet valve loaded by a valve spring, said inlet and outlet valves being actuated by transmission elements driven by a camshaft, said engine further comprising a hydraulic valve lash adjusting element which is installed in at least one of said transmission elements or in a component which is installed in the transmission element between the camshaft and at least one inlet and/or outlet valve, said engine further comprising a hydraulic valve lash adjusting element comprising a working piston, a cylinder housing interacting with said working piston, a resetting spring arranged in between, and a non-return valve which delimits a high pressure chamber, and a valve closing body of said non-return valve corresponding to a valve seat on said working piston.

BACKGROUND

Reciprocating piston internal combustion engines with hydraulic valve lash adjusting elements of the generic type are well known. A problem of such engines is that, depending on the speed of rotation of the reciprocating piston, internal combustion engine and the lift height of the cams, the high pressure chamber of the valve lash adjusting elements is not capable of being sufficiently filled, so that a sinking of the hydraulic valve lash adjusting element can occur and this leads to enhanced or impermissibly large lash in the valve train. On the other hand, it is also possible that the hydraulic valve lash adjusting element gets excessively pumped up, so that valve lash falls short of the permissible value.

It is known, see DE 10 2007 014 248 A1, to provide stop and clamping devices on the hydraulic valve lash adjusting element that are externally activated and prevent both a pumping-up as also a sinking of the hydraulic valve lash adjusting element. Stop and clamping devices of this type are structurally very complex and cost intensive.

The problems are of particular importance when, in addition to the hydraulic valve lash adjusting elements, brake control devices or exhaust gas return devices are also used on the reciprocating piston internal combustion engine with provision of additional cam lobes in the region of the base circle of the cams.

SUMMARY

It is therefore an object of the invention to eliminate the drawbacks of the aforesaid measures on hydraulic valve lash adjusting elements particularly with the aim that, both during normal operation, particularly in the case of large engines for utility vehicles, as also during operations with additional opening of the gas exchange valves for decompression or exhaust gas return purposes, no sinking of the hydraulic valve lash adjusting elements occurs. This should be achieved using simple means.

The invention achieves the above object by the fact that the valve closing body comprises a partial spherical surface in the region of the valve seat and that the ratio of the diameter of the working piston (8) to twice the radius of the partial spherical surface (13) is ≦2.

In this way, it is achieved that the valve seat, or the valve closing body, possesses a large opening in the region of the valve seat without the overall dimensions of the valve closing body being disproportionately large. This enables an adequate and rapid filling of the high pressure chamber, so that a sinking of the hydraulic valve lash adjusting element is prevented and this, even when additional lobes on the cam shorten the filling time considerably.

Adjoining the partial spherical surface, the valve closing body comprises a cylindrical peripheral surface starting from the edge of the spherical surface. Through this measure, the valve closing body has a light weight which, in contrast to usual valve closing bodies configured as balls, manifests a considerably smaller mass although the valve seat has a large diameter.

According to a further development of the invention, the valve closing body comprises following the cylindrical peripheral surface, a peg and this peg is surrounded by a valve closing spring that is further supported in an opening of a valve cap. In this way, an additional guidance is created for the valve closing body.

As proposed by the invention, a bore, preferably a stepped bore is arranged adjoining the opening in the valve cap, so that the high pressure chamber can get filled even along the valve closing spring, the peg and the stepped bore.

According to a further proposition of the invention, a pocket hole is arranged in the region of the partial spherical surface on the end of the valve closing body turned away from the peg. This pocket bore is a further contribution to a reduction of the mass of the valve closing body and an enlargement of the oil reservoir. The pocket hole also serves as a collecting pocket for contaminants in the oil.

In a further development of the invention, the radius of the closing spherical surface is larger than or equal to 2.5 mm.

In this case, the valve seat diameter is larger than or equal to 5.0 mm, and the diameter of the valve closing body is larger than or equal to 7.5 mm. This assures a complete filling of the high pressure chamber even in the presence of intermediate lobes in the region of the base circle of the cams.

This is based on the fact that the diameter of the working piston and that of the opening cross-section of the non-return valve are of special importance for the mode of functioning of the hydraulic valve lash adjusting element.

The valve cap is advantageously configured with a stepped inner diameter, and the large diameter surrounds the outer peripheral surface of the valve closing body, while the smaller diameter surrounds the valve closing spring.

Beads and openings are arranged on the valve cap in the region of the large diameter and extend from the high pressure chamber to the valve seat in order to assure an adequate and rapid filling of the high pressure chamber.

BRIEF DESCRIPTION OF THE DRAWINGS

For a further elucidation of the invention reference will be made to the appended drawings in which one example of embodiment is shown in simplified illustrations.

FIG. 1 shows a section through a rocker arm configured as a transmission element comprising a hydraulic valve lash adjusting element that is connected through a roller with a cam of a camshaft, and

FIG. 2 shows a section through the hydraulic valve lash adjusting element on an enlarged scale.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As far as specifically illustrated in FIGS. 1 and 2, a rocker arm pivotally mounted on a rocker arm axle 2 is identified at 1. The rocker arm 1 is operatively connected through a roller 3 to a cam 4 of a reciprocating piston internal combustion engine. The cam is a component part of a camshaft that is designed for use in a reciprocating piston internal combustion engine for a utility vehicle and/or a passenger vehicle.

On the free end of the rocker arm 1 is installed a hydraulic valve lash adjusting element generally identified at 5 that is supplied through a channel with oil from the reciprocating piston internal combustion engine and/or another oil supply unit.

The hydraulic valve lash adjusting element 5 comprises a cylindrical housing 7 that is guided for sliding in the rocker arm 1. Within the cylindrical housing 7 is installed a working piston 8 whose outward movement in the cylindrical housing 7 is limited by a spring ring. The working piston 8 is supported, as shown in FIG. 1, on an end plate 9 that is fixed in the rocker arm 1. A hollow space configured within the working piston 8 to serve as a reservoir 10 for oil is adjoined by a valve seat 11 to which a valve closing body 12 is associated. The valve closing body 12 comprises a partial spherical surface 13 that merges into a cylindrical peripheral surface 14. Adjoining the cylindrical peripheral surface 14 is integrally formed on the valve closing body 12, a peg 15 that is surrounded by a valve closing spring 16. The valve closing spring 16 is further supported on a valve cap 17 that is firmly installed in the working piston, for example, by pressing. A resetting spring 18 is arranged between the valve cap 17 and the cylindrical housing 7 to bias the working piston away from the cylindrical housing 7. The space around the resetting spring 18 is configured as a high pressure chamber 19 that is controlled by the valve closing body 12 that prevents a compression of the high pressure chamber. In the wall of the valve cap 17 surrounding the valve closing body 12 are arranged beads 20 and openings 21 that assure a rapid filling of the high pressure chamber 19 out of the reservoir 10.

On the end of the valve closing body 12 turned away from the peg 15 is configured a pocket hole 22 through which the mass of the valve closing body is reduced, the reservoir 10 at the same time enlarged and a collecting pocket formed in which contaminants of the oil can get deposited.

Finally, it may be pointed out once again that, normally, the ratio of the diameter of the working piston to the diameter of the valve closing body, which is normally configured as a ball, is situated above a value of 3. In the present case, the ratio for a constant diameter of the working piston and a radius of the partial spherical surface of r=4 is ≦2.

LIST OF REFERENCE NUMERALS

-   1 Rocker arm -   2 Rocker arm axle -   3 Roller -   4 Cam -   5 Hydraulic valve lash adjusting element -   6 Channel -   7 Cylindrical housing -   8 Working piston -   9 End plate -   10 Reservoir -   11 Valve seat -   12 Valve closing body -   13 Partial spherical surface -   14 Cylindrical peripheral surface -   15 Peg -   16 Valve closing spring -   17 Valve cap -   18 Resetting spring -   19 High pressure chamber -   20 Beads -   21 Openings -   22 Pocket hole 

1. A four stroke reciprocating piston internal combustion engine comprising a crankcase and at least one cylinder arranged in said crankcase, a piston is guided in the cylinder by a crankshaft, at least one cylinder head closing said cylinder, intake and exhaust channels of said cylinder head being controlled in each case by at least one intake and exhaust valve loaded by a valve spring, said intake and exhaust valves being actuated by transmission elements driven by a camshaft, a hydraulic valve lash adjusting element is installed in at least one of said transmission elements or in a component which is installed in the transmission element between the camshaft and at least one of the intake or exhaust valves, the hydraulic valve lash adjusting element comprising a working piston, a cylinder housing interacting with said working piston, a resetting spring arranged in between, and a non-return valve which delimits a high pressure chamber, and a valve closing body of said non-return valve corresponding to a valve seat on said working piston, the valve closing body comprises a partial spherical surface in a region of the valve seat and a ratio of a diameter of the working piston to twice a radius of the partial spherical surface is ≦2.
 2. A four stroke reciprocating piston internal combustion engine comprising a crankcase and at least one cylinder arranged in said crankcase, a piston is guided in the cylinder by a crankshaft, at least one cylinder head closing said cylinder, intake and exhaust channels of said cylinder head being controlled in each case by at least one intake and outlet valve loaded by a valve spring, said intake and exhaust valves being actuated by transmission elements driven by a camshaft, a hydraulic valve lash adjusting element is installed in at least one of said transmission elements or in a component which is installed in the transmission element between the camshaft and at least one of the intake or exhaust valves, a hydraulic valve lash adjusting element comprising a working piston, a cylinder housing interacting with said working piston, a resetting spring arranged in between, and a non-return valve which delimits a high pressure chamber, and a valve closing body of said non-return valve corresponding to a valve seat on said working piston, the valve closing body comprises in a region of the valve seat, a partial spherical surface which is adjoined by a cylindrical peripheral surface.
 3. A four stroke reciprocating piston internal combustion engine comprising a crankcase and at least one cylinder arranged in said crankcase, a piston is guided in the cylinder by a crankshaft, at least one cylinder head closing said cylinder, intake and exhaust channels of said cylinder head being controlled in each case by at least one intake and exhaust valve loaded by a valve spring, said intake and exhaust valves being actuated by transmission elements driven by a camshaft, a hydraulic valve lash adjusting element is installed in at least one of said transmission elements or in a component which is installed in the transmission element between the camshaft and at least one of the intake or exhaust valves, said engine further comprising a hydraulic valve lash adjusting element comprising a working piston, a cylinder housing interacting with said working piston, a resetting spring arranged in between, and a non-return valve which delimits a high pressure chamber, and a valve closing body of said non-return valve corresponding to a valve seat on said working piston, a diameter of the valve seat is ≧5.0 mm.
 4. A four stroke reciprocating piston internal combustion engine comprising a crankcase and at least one cylinder arranged in said crankcase, a piston is guided in the cylinder by a crankshaft, at least one cylinder head closing said cylinder, intake and exhaust channels of said cylinder head being controlled in each case by at least one intake and exhaust valve loaded by a valve spring, said intake and exhaust valves being actuated by transmission elements driven by a camshaft, said engine further comprising a hydraulic valve lash adjusting element is installed in at least one of said transmission elements or in a component which is installed in the transmission element between the camshaft and at least one of the intake or exhaust valves, a hydraulic valve lash adjusting element comprising a working piston, a cylinder housing interacting with said working piston, a resetting spring arranged in between, and a non-return valve which delimits a high pressure chamber, and a valve closing body of said non-return valve corresponding to a valve seat on said working piston, a diameter of the valve closing body is ≧7.5 mm.
 5. A four stroke reciprocating piston internal combustion engine comprising a crankcase and at least one cylinder arranged in said crankcase, a piston is guided in the cylinder by a crankshaft, said engine further comprising at least one cylinder head closing said cylinder, intake and exhaust channels of said cylinder head being controlled in each case by at least one intake and exhaust valve loaded by a valve spring, said intake and exhaust valves being actuated by transmission elements driven by a camshaft, said engine further comprising a hydraulic valve lash adjusting element is installed in at least one of said transmission elements or in a component which is installed in the transmission element between the camshaft and at least one of the intake or exhaust valves, a hydraulic valve lash adjusting element comprising a working piston, a cylinder housing interacting with said working piston, a resetting spring arranged in between, and a non-return valve which delimits a high pressure chamber, and a valve closing body of said non-return valve corresponding to a valve seat on said working piston, the valve closing body comprises a partial spherical surface, a pocket hole turned away from the high pressure chamber is arranged in a region of the partial spherical surface.
 6. A reciprocating piston internal combustion engine according to claim 1, wherein the radius of the partial spherical surface is ≧2.5 mm.
 7. A reciprocating piston internal combustion engine according to claim 2, wherein adjoining the cylindrical peripheral surface, the valve closing body comprises a peg.
 8. A reciprocating piston internal combustion engine according to claim 7, wherein the peg is surrounded by a valve closing spring that is further supported in an opening of a valve cap.
 9. A reciprocating piston internal combustion engine according to claim 8, wherein a bore, is arranged adjoining the opening in the valve cap.
 10. A reciprocating piston internal combustion engine according to claim 8, wherein the valve cap is configured with a stepped inner diameter, having a large inner diameter surrounding the cylindrical peripheral surface of the valve closing body and a smaller diameter surrounding the valve closing spring.
 11. A reciprocating piston internal combustion engine according to claim 10, wherein beads or openings are arranged on the valve cap in a region of the large diameter and extend from the high pressure chamber to the valve seat. 